Cobalt is an essential element found principally in vitamin B12 (cyanocobalamin). Determination of nutritional adequacy is therefore more conveniently assessed through measurement of plasma vitamin B12.
Exposure to cobalt and its compounds occurs in the hard metal industry, cobalt refineries, specialist alloy manufacture, magnet manufacturing, the paint industry and in diamond tooling.24 The main effects noted in humans result from dust inhalation and skin contact. Prolonged inhalation can result in respiratory sensitisation and asthma, and skin contact can lead to allergic dermatitis. Although it does not accumulate in the body, chronic ingestion of cobalt can result in cardiomyopathy.
Measurement of urinary cobalt concentrations on samples collected at the end of a working shift can be used as a guide to exposure.25 It has a very short half-life and after exposure urine concentrations can drop to normal concentrations within 2 to 3 days.
Measurement of chromium and cobalt in whole blood is used to assess the viability of metal-on-metal knee and hip joint implants. The Medical and Health Regulatory Agency (MHRA) has issued advice on monitoring patients.20 The toxic effects, such as tissue damage, pseudo-tumour and soft tissue necrosis around the site of the implant, are thought to be due to cobalt ions.
Sample Requirements and Reference Ranges for Cobalt
|Sample Type||Whole blood, urine (random)|
Urine: universal container
|Precautions||Urine samples for occupational exposure should be taken as random samples at the end of a working shift.|
Whole blood: 300 µL* (Cr can be analysed simultaneously on this volume).
Urine: 1 mL
Blood: < 50 nmol/L23
MHRA action limit: 120 nmol/L (7 µg/L)20
N.B. MHRA threshold does not apply to stemmed total hip replacementsUrine: < 1.6 nmol/mmol creatinine11
|Mean Turnaround time||Blood: 3.7 days; urine: 5.5 days|
Inductively coupled plasma mass spectrometry
Blood: Traceable to reference material produced in accordance with EN ISO 17511:2003 “In vitro diagnostic medical devices. Measurement of quantities in biological samples. Metrological traceability of values assigned to calibrators and control materials”.
Urine: Traceable to reference material produced in accordance with EN ISO 17511:2003 “In vitro diagnostic medical devices. Measurement of quantities in biological samples. Metrological traceability of values assigned to calibrators and control materials” and reference materials with values determined by reference laboratories.
|Intermediate Precision (CV)||
Blood: 14.9% at 2.6 nmol/L, 4.1% at 184 nmol/L
Urine: 7.4% at 30.8 nmol/L, 1.4% at 521 nmol/L
|Measurement Uncertainty, U||
Blood: 89 ± 3.7 nmol/L, 179 ± 8.0 nmol/L
Urine: 33.2 ± 2.0 nmol/L, 578 ± 33.6 nmol/L
|Analytical Goals (CV)||Blood: 5%**, Urine: 5%**|
|EQA Scheme||Blood and urine: UK NEQAS, Guildford (once per month)|
* Absolute minimum volume; this volume is insufficient to carry out repeat analysis if analysis fails.
** Goal Origin: STEMDRL state-of-the-art